Investigation of the splitting tensile performance of Rock-Filled Concrete based on mesoscopic modeling: Effects of the interfacial transition zone and rockfill characteristics

Research on the Stability of Arc-Fractured Rock–Concrete Composites: Mechanical Response and Energy Evolution

To mitigate the violent movement of overlying strata in goaf areas, rock–concrete composite support systems are widely utilized. However, the mechanical behavior of such systems under the influence of complex pre-existing defects, such as arc-shaped fractures, remains insufficiently understood. This study aims to clarify the failure mechanisms and the evolution of stability in these composites by evaluating the influence of fracture inclination angles. A synergistic methodology was adopted, combining laboratory uniaxial compression tests with discrete-element method simulations. Based on energy dissipation theory and the strain equivalence hypothesis, a statistical damage constitutive model was established to bridge the gap between microscopic damage and macroscopic mechanical response. The results demonstrate that fracture inclination significantly dictates the energy partitioning and crack propagation patterns within the composite. The established constitutive model, validated by numerical results ( R 2 > 0.999), effectively quantifies how increasing inclination angles enhance energy absorption efficiency and retard structural damage progression. Due to the high toughness of the concrete component, the composite maintains substantial residual bearing capacity, preventing instantaneous failure. These findings provide a robust theoretical framework and practical guidance for optimizing support designs in deep underground excavations with intricate geological defects.

Study on the properties of TiC, Nano-CaCO3, and steel fiber reinforced concrete based on RSM-BBD: optimization of mechanical properties.

As modern civil engineering demands increasingly higher strength, toughness, and long-term stability from concrete materials, the performance limitations of ordinary concrete in complex service environments have become increasingly apparent. The dual-blending modification of nanomaterials and steel fibers (SF) has emerged as an effective technical approach to overcome these limitations. The ratio design of the TiC-NC-SF dual-blending system has largely relied on empirical methods, lacking systematic quantitative optimization. The synergistic mechanisms among multiple factors remain unclear, hindering the engineering application of modified concrete. This study employs Box-Behnken experimental design and response surface methodology to systematically investigate the influence patterns of three factors on concrete's 28-day compressive strength, splitting tensile strength, and flexural strength. Scanning electron microscopy (SEM) characterization reveals microstructural mechanisms, while model optimization validates optimal ratios. Results indicate the dominance order of the three factors on concrete mechanical properties is SF > NC > TiC (with NC and TiC having similar effects on compressive strength). A significant synergistic enhancement effect exists between TiC and NC (interaction term P < 0.05). Both TiC and NC enhance concrete strength by optimizing matrix density through "hydration regulation and multi-level filling," while SF dominates crack control via "bridging crack propagation and energy dissipation toughening." No significant interaction was observed between TiC-SF or NC-SF (P > 0.05). Concrete compressive strength exhibits a quadratic variation with increasing dosage of all three factors, with SF exerting greater influence on splitting tensile strength and flexural strength. The response surface model optimization yielded the optimal mix design of TiC 2.12%, NC 2.14%, and SF 1.19%. Its 28-day compressive strength, splitting strength, and flexural strength reached 69.83 MPa, 7.22 MPa, and 9.34 MPa, respectively (measured values). The response surface optimization values were 70.50 MPa, 7.52 MPa, and 9.60 MPa, respectively. According to the experimental results, these values increased by 22.66%, 26.44%, and 15.02%, respectively, compared with the control group (CG). The performance deviation from the optimal experimental group was less than 0.5%, and the deviation from the optimization target was within 10%. SEM characterization revealed that the cement matrix in the CN10 and CN18 groups exhibited significantly higher densification than the CG group, with SF tightly bonded to the matrix interface.

A Comparative Study on Crack-bridging and Microstructural Densification Mechanisms Governing the Mechanical Properties of Fly-ash-based M25 Concrete Modified with MWCNT AND SiO2 NPS

This study examines the mechanical, microstructural, and hydration-related improvements in concrete modified with fly ash, multi-walled carbon nanotubes (MWCNTs), and nano silica. A comprehensive experimental program, comprising compressive, split tensile, and flexural strength tests along with SEM and XRD analyses, was conducted to evaluate the combined and individual effects of these additives. Fly ash improved the sustainability and long-term performance of concrete through its pozzolanic reaction, although its early-age strength contribution remained moderate. The inclusion of MWCNTs produced the most pronounced mechanical enhancements, with the 0.45% dosage yielding peak strength values due to efficient crack-bridging, improved stress transfer, and accelerated hydration. Nano silica also contributed to performance enhancement by refining pore structure and promoting the formation of a dense C–S–H matrix, with strength increasing progressively with higher dosages. The SEM images confirmed the development of a dense and compact microstructure, while XRD patterns displayed reduced portlandite peaks and enhanced amorphous C–S–H formation in nano-modified mixes. The findings demonstrate that nano-engineered additives, especially MWCNTs, significantly enhance the microstructure, mechanical strength, and durability of the concrete, highlighting their potential for producing high-performance and advanced composite materials.

Grain-scale failure mechanism of heterogeneous rock under tensile loading: insights from image-based DEM modeling

Experimental investigation on mechanical properties of backfill–rock composite structure under in-situ mining and filling stress loading

Impacts of Water Saturation on the Mechanical Behavior of Basalt/Glass Fiber-Reinforced Recycled Aggregate Concrete Under Varying Stresses: Insights from Macro and Micro Perspectives

Recycled aggregate concrete (RAC) offers an effective approach to reducing the environmental burden associated with construction and demolition waste. In this study, a fiber-reinforced RAC was developed by replacing part of the cement with fly ash and ground granulated blast-furnace slag, while glass fibers or basalt fibers were incorporated as reinforcing materials. A systematic experimental program was conducted to evaluate the mechanical behavior of the proposed concrete under different saturation conditions. The results show that the best toughness performance was achieved in the natural moisture state. In comparison, compressive and flexural strengths reached their maximum values under dry conditions, whereas splitting tensile strength peaked in the natural state. Based on the experimental data, prediction equations were established for the splitting tensile and flexural strengths by considering both saturation degree and fiber content. A stress–strain model under uniaxial compression was also developed. In addition, scanning electron microscopy (SEM) was employed to examine the fiber–matrix interface and hydration products, thereby clarifying the microstructural characteristics of the concrete at different saturation levels.